couple of questions

[sharpe]

Hi, i have a coupe of question.


1. What sort of external earth block is used for an external MEB, used to connect the MEC and a sub-mains earth on a TNS system?


https://www.tlc-direct.co.uk/Products/TLEB8.html



Is this what i am looking for or am i barking up the wrong tree. Does it need to be fixed inside an enclosure?


2. Does a switch fuse always have to be rated lower than the main cutout? Or can it be equivalent to the main cutout?


For example on a 60a main cut out, does the switchfuse used to supply the sub-mains have to be 60a or less?

 

[malcolmsanford]

Hi, i have a coupe of question.


1. What sort of external earth block is used for an external MEB, used to connect the MEC and a sub-mains earth on a TNS system?


https://www.tlc-direct.co.uk/Products/TLEB8.html



Is this what i am looking for or am i barking up the wrong tree. Does it need to be fixed inside an enclosure That is the correct earth bar. As the Earthing conductor is not a "live" there is no need to put it into an enclosure. If it is you MET you will need to label it as such.


2. Does a switch fuse always have to be rated lower than the main cutout? Or can it be equivalent to the main cutout?


For example on a 60a main cut out, does the switchfuse used to supply the sub-mains have to be 60a or less? Do you know what the BS fuse is inside your main cut out? What is the sub mains feeding? What is your loading on the sub main? There are far too many questions. But it is not good practice normally not to have some discrimination between protection devices.

See red

 

[sharpe]

When the DNO came out to install the 100a double pole isolator, they said that the cutout was 60a like all the supplies round here and it could cope with the sub-mains. In fact the engineer said that the cutout would be able to cope with 80a plus, which was a little confusing.

The sub mains is feeding the garage. The loading in the garage is a 40a 30ma RCCB, with a 6a radial and 32a ring circuit.

 

[malcolmsanford]

He most likely meant that the header can take either a 60 or 80 amp BS fuse.

You have answered your own question really, that 40amp RCBO is less than the 60amp main fuse

Is there a real need for wiring a ring final in the garage...............

 

[Dave OCD]

What size is the sub-main cable to the garage ? If it's only a ring and lighting circuit a 40a OCPD at the sourcce would be more than adequate surely ?

 

[davesparks]

With a 40A rccb in the garage it would be unwise to protect it with anything bigger than a 40A ocpd